| 1 | import Foundation |
| 2 | import XCTest |
| 3 | import RastrilloNative |
| 4 | |
| 5 | final class BackoffTests: XCTestCase { |
| 6 | func testDoublesFromHalfASecondToTenWithEqualJitter() { |
| 7 | var high = Backoff(random: { $0.upperBound }) |
| 8 | XCTAssertEqual((0..<7).map { _ in high.next() }, [0.5, 1, 2, 4, 8, 10, 10]) |
| 9 | var low = Backoff(random: { $0.lowerBound }) |
| 10 | XCTAssertEqual((0..<6).map { _ in low.next() }, [0.25, 0.5, 1, 2, 4, 5]) |
| 11 | var real = Backoff() |
| 12 | for expected in [0.5, 1.0, 2.0, 4.0] { |
| 13 | let delay = real.next() |
| 14 | XCTAssertTrue((expected / 2...expected).contains(delay), "\(delay) outside [\(expected / 2), \(expected)]") |
| 15 | } |
| 16 | } |
| 17 | |
| 18 | func testRetryAfterIsAFloorCappedAtFiveMinutes() { |
| 19 | var backoff = Backoff(random: { $0.upperBound }) |
| 20 | XCTAssertEqual(backoff.next(retryAfter: 30), 30) |
| 21 | XCTAssertEqual(backoff.next(retryAfter: 3600), 300) |
| 22 | XCTAssertEqual(backoff.next(retryAfter: 0.1), 2, "A short Retry-After must not undercut the backoff") |
| 23 | } |
| 24 | |
| 25 | func testResetsOnSuccessAndAfterAStableConnectionOnly() { |
| 26 | var backoff = Backoff(random: { $0.upperBound }) |
| 27 | _ = backoff.next(); _ = backoff.next(); _ = backoff.next() |
| 28 | backoff.opened(at: 100) |
| 29 | backoff.ended(at: 103) |
| 30 | XCTAssertEqual(backoff.next(), 4, "A connection that dropped quickly must keep backing off") |
| 31 | backoff.opened(at: 200) |
| 32 | backoff.ended(at: 206) |
| 33 | XCTAssertEqual(backoff.next(), 0.5) |
| 34 | _ = backoff.next() |
| 35 | backoff.reset() |
| 36 | XCTAssertEqual(backoff.next(), 0.5) |
| 37 | } |
| 38 | |
| 39 | /// The stable clock starts when the stream opens, not when the attempt |
| 40 | /// starts: a slow refusal or a long access check must not count. |
| 41 | func testAnAttemptThatNeverOpenedIsNeverStable() { |
| 42 | var backoff = Backoff(random: { $0.upperBound }) |
| 43 | _ = backoff.next(); _ = backoff.next() |
| 44 | backoff.ended(at: 1_000) |
| 45 | XCTAssertEqual(backoff.next(), 2, "An attempt that never opened reset the backoff") |
| 46 | backoff.opened(at: 2_000) |
| 47 | backoff.ended(at: 2_006) |
| 48 | _ = backoff.next() |
| 49 | backoff.ended(at: 9_000) |
| 50 | XCTAssertEqual(backoff.next(), 1, "An earlier open was counted for a later attempt") |
| 51 | } |
| 52 | } |
| 53 | |
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